1. Field
This disclosure relates to a negative active material for a rechargeable lithium battery and a rechargeable lithium battery including the same.
2. Description of the Related Art
Lithium rechargeable batteries have recently drawn attention as a power source for small portable electronic devices. They use an organic electrolyte solution and thereby, have twice higher the discharge voltage than a conventional battery using an alkali aqueous solution, and accordingly, have high energy density.
As for positive active materials of a rechargeable lithium battery, there has been research on a lithium-transition element composite oxide that can intercalate lithium, such as LiCoO2, LiMn2O4, LiNi1−xCoxO2 (0<x<1), and so on.
On the other hand, negative active materials of a rechargeable lithium battery have included various carbon-based materials such as artificial graphite, natural graphite, and hard carbon, which can all intercalate and deintercalate lithium ions.
In addition, as a battery is increasingly required to have high energy density, much attention is drawn to a material that can be alloyed with lithium, for example, Si, Sn, Ge, oxides thereof, and alloys thereof, as a negative active material with high theoretical capacity density. In particular, a Si oxide has good cycle-life characteristics, and has been widely researched. However, the Si oxide has a problem that oxygen reacts with lithium (Li) and thus forms Li2O (lithium oxide). Accordingly, it may not only increase irreversible capacity but may also deteriorate energy density of a battery in order to compensate lithium. Furthermore, the Li2O that does not participate in charge and discharge expands an electrode and may deteriorate energy density. Therefore, it is possible to improve energy density without such compensation of lithium. In addition, since the Li2O include an alkali component, it reacts with an electrolyte particularly at a high temperature atmosphere and thereby may bring about a problem of generating gas, deteriorating capacity, and the like.